Re: How much does the human body temperature have to rise before sweating occur

Although the sweating helps to maintain the body temperature, it is not 
the only reason for stimulation of sweating. For example, as soon as we 
enter sunny area, we may start sweating. On the contrary, sweating may not 
occur even when the body temperature is elevated as in case of fever. 
Also, even if we move into hotter environment, body temperature does not 
usually rise so easily. As a measure of precaution, the temperature is 
sensed by the skin and before the body temperature raises, necessary 
action is taken by the system. 

Sweating occurs when the change in temperature is abrupt. Sweating and 
evoporation of sweat are in equilibrium when the temperature is 
maintained at certain level. When the ambient temperature rises, the 
equilibrium is lost. Hence, the skin senses the rise in temperature and 
starts sweating to compensate for the rise in temperature. Another 
reason for sweating is humidity, which inhibits evoporation of the sweat 
leading to inefficient cooling of the body, which further leads to more 
sweating.

The rise in body temperature may also occur due to strain or stress, 
which leads to increased metabolic activities. Locally, temperature can 
rise upto several degrees. However, sweating is stimulated in such 
situations not just by the temperature. Changes in hormonal activities 
during such stress conditions are responsible for stimulation of sweat 
glands.

Hence, many things such as temperature, physical excercise, fear, strain, 
etc. work together for stimulating sweat glands. Under normal 
circumstances, abrupt change in temperature of the environment of about 3-5 deg 
C can stimulate sweating.